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Jan 2008

Volume 26, Issue 1, pp. 1-183

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Conventional triode ionization gauge with carbon nanotube cold electron emitter

Lin Xiao, Li Qian, Yang Wei, Liang Liu, and Shoushan Fan

J. Vac. Sci. Technol. A 26, 1 (2008); http://dx.doi.org/10.1116/1.2803713 (4 pages) | Cited 2 times

Online Publication Date: 14 December 2007

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The authors presented a conventional triode ionization gauge with a linear-type carbon nanotube cold electron emitter, which was made by painting technology on a nickel wire. The gauge used the ratio of the ion current to the electron current to indicate the vacuum. Although there was fluctuation in the cathode’s emission current, the ratio of the ion current to the electron current kept stable with a variation of about ±10% in each pressure decade from 10−7 to 10−3 torr. The gauge showed good measurement linearity in the vacuum range from 10−6 to 10−3 torr.
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84.47.+w Vacuum tubes
61.46.Fg Nanotubes
81.65.-b Surface treatments
79.70.+q Field emission, ionization, evaporation, and desorption

Thermotunnel refrigerator with vacuum/insulator tunnel barrier: A theoretical analysis

Avto Tavkhelidze, Vasiko Svanidze, and Leri Tsakadze

J. Vac. Sci. Technol. A 26, 5 (2008); http://dx.doi.org/10.1116/1.2803717 (3 pages) | Cited 4 times

Online Publication Date: 14 December 2007

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The authors use two insulator layers in thermotunnel refrigerator to modify the shape of the tunneling barrier so that electrons with high kinetic energy pass it with increased probability. Theoretical analysis show that the overall tunneling current between the electrodes contains an increased number of high kinetic energy electrons and a reduced number of low energy ones, leading to high efficiency. The particular case of vacuum gap and solid insulator layer is calculated using digital methods. Efficiency remains high in the wide range of the emitter electric field. The cooling coefficient is found to be as high as 40%−50% in the wide range of the emitter electric field.
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07.30.-t Vacuum apparatus
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Damage-free microwave-excited plasma etching without carrier deactivation of heavily doped Si under thin silicide layer

Tetsuya Goto, Kazuyuki Ikenaga, Akinobu Teramoto, Masaki Hirayama, Shigetoshi Sugawa, and Tadahiro Ohmi

J. Vac. Sci. Technol. A 26, 8 (2008); http://dx.doi.org/10.1116/1.2804424 (9 pages) | Cited 3 times

Online Publication Date: 14 December 2007

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Microwave-excited high-density plasma etching equipment with a dual shower-plate structure has been developed to overcome various disadvantageous of current reactive-ion etching equipment. Disadvantages include severe charge-up damage, heavy dependence of etching speed on pattern size, and very limited etching conditions, where the plasma uniformity over the entire wafer surface is only maintained for predetermined gas species, gas working pressure, self-bias voltage, and wafer surface patterns and materials. The authors’ new system has been confirmed to be free from charge-up damage, have pattern-size-dependent etching speed, and maintain the plasma uniformity over the entire wafer surface even if gas species, gas working pressure, self-bias voltage, and wafer surface patterns and materials are changed. To establish damage-free contact-hole etching without degradation of contact resistance of source and drain electrodes of metal-oxide-semiconductor transistors, damage of heavily doped Si induced by ion bombardment through the silicide (TaSi2) is investigated by using this new system. Carrier deactivation and Si lattice damage are found at the heavily doped Si layer even by ion-bombardment through the silicide when the energy of the bombarding ions to the wafer surface is larger than the critical value, which depends on gas species and frequency of rf power applied to the wafer electrode. Highly productive damage-free etching has been established for source and drain contact-hole etching by combining high-speed etching and damage-free etching using this new system, where the self-bias voltage is set at high voltages for high-speed etching and decreased to −300 to −500 V for damage-free etching at the final stage of contact-hole etching. In this new system, the plasma uniformity is widely maintained even if the self-bias voltage is widely varied during processes.
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85.30.Tv Field effect devices
81.65.Cf Surface cleaning, etching, patterning

Experimental studies of Ge1−xCx and Ge1−x−yCxAly thin films

R. J. Soukup, J. L. Huguenin-Love, N. J. Ianno, and D. W. Thompson

J. Vac. Sci. Technol. A 26, 17 (2008); http://dx.doi.org/10.1116/1.2805244 (6 pages)

Online Publication Date: 14 December 2007

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Experimental results on thin films of the materials GexC1−x, and Ge1−x−yCxAly deposited by a unique multiplasma hollow cathode sputtering technique, are presented. These films have been characterized by several techniques, the most important being in situ and ex situ spectroscopic ellipsometry, Auger electron spectroscopy (AES), and x-ray diffraction (XRD). The spectroscopic ellipsometry measurements of the films indicate that this material is a very strong absorber of photons. The XRD measurements reveal that the carbon is entering the lattice in substitutional sites, to a certain extent, and the AES depth profiling measurements determine the concentration and location of the different constituents. The materials appear to grow such that the concentration of the different elements is uniform throughout the films. The photon absorption inferred from the ellipsometry measurements corroborated the fact that GeC has a photon absorption efficiency much greater than crystalline Si or Ge and even more than amorphous Si in the wavelength range most useful for photovoltaic applications. In fact, the addition of aluminum increased this absorption efficiency substantially.
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78.66.Db Elemental semiconductors and insulators
79.20.Fv Electron impact: Auger emission

Physical vapor deposition synthesis of tungsten monocarbide (WC) thin films on different carbon substrates

E. C. Weigert, M. P. Humbert, Z. J. Mellinger, Q. Ren, T. P. Beebe, L. Bao, and J. G. Chen

J. Vac. Sci. Technol. A 26, 23 (2008); http://dx.doi.org/10.1116/1.2806941 (6 pages) | Cited 8 times

Online Publication Date: 14 December 2007

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The synthesis of tungsten monocarbide (WC) thin films has been performed by physical vapor deposition on various substrates including glassy carbon, carbon fiber sheet, carbon foam, and carbon cloth. The WC and W2C phase contents of these films have been evaluated with bulk and surface analysis techniques such as x-ray diffraction, x-ray photoelectron spectroscopy, and scanning electron microscopy. These characterization techniques were also used to determine the effects of synthesis by nonreactive and reactive sputtering. The synthesis of WC particles supported on the carbon fiber substrate has also been accomplished using the temperature programmed reaction method. Overall, the results demonstrate that the phase purity of tungsten carbides can be controlled by the deposition environment and annealing temperatures.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
81.15.Cd Deposition by sputtering

Thermal stability and thermo-mechanical properties of magnetron sputtered Cr-Al-Y-N coatings

Florian Rovere and Paul H. Mayrhofer

J. Vac. Sci. Technol. A 26, 29 (2008); http://dx.doi.org/10.1116/1.2806943 (7 pages) | Cited 10 times

Online Publication Date: 14 December 2007

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Cr1−xAlxN coatings are promising candidates for advanced machining and high temperature applications due to their good mechanical and thermal properties. Recently the authors have shown that reactive magnetron sputtering using Cr-Al targets with Al/Cr ratios of 1.5 and Y contents of 0, 2, 4, and 8 at % results in the formation of stoichiometric (Cr1−xAlx)1−yYyN films with Al/Cr ratios of ∼ 1.2 and YN mole fractions of 0%, 2%, 4%, and 8%, respectively. Here, the impact of Y on thermal stability, structural evolution, and thermo-mechanical properties is investigated in detail. Based on in situ stress measurements, thermal analyzing, x-ray diffraction, and transmission electron microscopy studies the authors conclude that Y effectively retards diffusional processes such as recovery, precipitation of hcp-AlN and fcc-YN, grain growth, and decomposition induced N2 release. Hence, the onset temperature of the latter shifts from ∼ 1010 to 1125 °C and the hardness after annealing at Ta = 1100 °C increases from ∼ 32 to 39 GPa with increasing YN mole fraction from 0% to 8%, respectively.
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68.60.Dv Thermal stability; thermal effects
81.15.Cd Deposition by sputtering
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.Qp Friction, tribology, and hardness
68.60.Bs Mechanical and acoustical properties
81.40.Gh Other heat and thermomechanical treatments

Fundamental reliability of 1.5‐nm-thick silicon oxide gate films grown at 150 °C by modified reactive ion beam deposition

Hiroshi Yamada

J. Vac. Sci. Technol. A 26, 36 (2008); http://dx.doi.org/10.1116/1.2812430 (8 pages)

Online Publication Date: 14 December 2007

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The reliability of 1.5‐nm-thick silicon oxide gate films grown at 150 °C by modified reactive ion beam deposition (RIBD) with in situ pyrolytic-gas passivation (PGP) using N2O and NF3 was investigated. RIBD uses low-energy-controlled reactive, ionized species and potentializes low-temperature film growth. Although the oxide films were grown at a low temperature of 150 °C, their fundamental indices of reliability, such as the time-dependent dielectric breakdown lifetime and interface state density, were almost equivalent to those of oxide films grown at 850 °C using a furnace. This is probably due to localized interfacial N and F atoms. The number density of interfacial N atoms was about seven times larger than that for the furnace-grown oxide films, and this is a key factor for improving the reliability through the compensation of residual inconsistent-state bonding sites.
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77.22.Jp Dielectric breakdown and space-charge effects
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
81.15.Jj Ion and electron beam-assisted deposition; ion plating
81.65.Rv Passivation

Stress evolution and defect diffusion in Cu during low energy ion irradiation: Experiments and modeling

Wai Lun Chan and Eric Chason

J. Vac. Sci. Technol. A 26, 44 (2008); http://dx.doi.org/10.1116/1.2812432 (8 pages) | Cited 7 times

Online Publication Date: 14 December 2007

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Measurements of stress generation in Cu during low energy ion irradiation show that the induced stress depends on temperature and ion flux. A steady-state compressive stress is observed during irradiation, which turns into tensile stress after the irradiation is stopped. The results cannot be explained by the incorporation of gas ions alone, and point defects generated by the ions must be considered. In this work, the authors develop a continuum model that includes ion implantation, sputtering, and defect diffusion to explain the experimental data. The authors show that the experimental results can be reproduced primarily by considering a difference in diffusivity between interstitials and vacancies.
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81.40.Lm Deformation, plasticity, and creep
61.80.Jh Ion radiation effects
66.30.Lw Diffusion of other defects

Silicon etch in the presence of a fluorocarbon overlayer: The role of fluorocarbon cluster ejection

Joseph J. Végh, David Humbird, and David B. Graves

J. Vac. Sci. Technol. A 26, 52 (2008); http://dx.doi.org/10.1116/1.2812444 (10 pages) | Cited 6 times

Online Publication Date: 14 December 2007

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Molecular dynamics (MD) simulations have been carried out to examine the role of large fluorocarbon (FC) cluster ejection during steady state Si plasma etching in the presence of a FC overlayer on the surface. Previous MD studies showed that the thickness of the FC film fluctuates during steady state Si etch, and that these fluctuations are an integral component of the Si etch mechanism. This work focuses on how the ejection of large FC clusters (containing six or more carbon atoms) contribute to FC film thickness fluctuations. Simulations reveal that ∼ 40%–60% of the carbon removal occurs through these clusters at steady state. Large FC cluster ejection was always observed when FC films form during etching. Product and kinetic energy distributions illustrate the effects of the plasma chemistry (i.e., the FC/F/Ar+ ratio impacting the surface) on the cluster ejection process. Further studies have also been carried out to examine the possibility of cluster redeposition on the surface and evaluate the likelihood of these large clusters contributing to FC film growth in typical plasma systems. Several clusters were found to have comparable (or even higher) sticking probability than the original FC deposition precursors. Overall, this work suggests that FC clusters play a key role in the Si etch process in these systems, and can also contribute to FC film growth. The effects of clusters in profile simulations and other plasma processing analyses may be more important than previously thought.
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81.65.Cf Surface cleaning, etching, patterning

Oxygen adsorption on Ag/Si(111)‐7×7 surfaces

Zhen Zhang, Jian Jiao, Zhiquan Jiang, Dali Tan, Qiang Fu, Xinhe Bao, Xi Liu, Jinfeng Jia, and Qikun Xue

J. Vac. Sci. Technol. A 26, 62 (2008); http://dx.doi.org/10.1116/1.2816938 (6 pages) | Cited 2 times

Online Publication Date: 14 December 2007

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The growth of Ag clusters on Si(111)‐7×7 surfaces was studied by scanning tunneling microscopy (STM), ultraviolet photoelectron spectroscopy, and x-ray photoelectron spectroscopy (XPS). A shift in the Ag 3d binding energy and a noticeable change in the valence-band structure reveal a significant modification of the electronic states of the Si(111)‐7×7 surface and the dispersed Ag clusters, which had a strong dependence on the coverage of Ag. Furthermore, these Ag clusters deposited on the Si surface alter the behavior of oxygen adsorption on the Si(111)‐7×7 surface. As evidenced by XPS, the presence of Ag inhibits the adsorbed surface oxygen species, the ins-ins and ad-ins oxygen, in which “ad” denotes an O atom bonding on top of the Si adatom and “ins” denotes an O atom inserted into a Si adatom back bond. The STM and high-resolution electron energy loss spectroscopy results show that the ins-ins oxygen species are more significantly suppressed by the Ag clusters compared to the ad-ins oxygen.
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68.43.Mn Adsorption kinetics
68.47.De Metallic surfaces
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
79.60.Dp Adsorbed layers and thin films
79.20.Uv Electron energy loss spectroscopy

Tritium migration along the cryopumping section

Oleg B. Malyshev

J. Vac. Sci. Technol. A 26, 68 (2008); http://dx.doi.org/10.1116/1.2816945 (10 pages) | Cited 3 times

Online Publication Date: 14 December 2007

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The transport section of the Karlsruhe Tritium Neutrino experiment (KATRIN) must provide the dramatic reduction of tritium flow and gas density from the end of a 10-m-long windowless gaseous tritium source throughout several stages of a differential pumping system. The final stage of this section, the cryogenic pumping section (CPS) based on pumping of tritium on argon frost at 4.5 K, should provide the flow ratio between inlet and outlet in the range of 107. Cryosorbed tritium may decay, emitting a few keV electrons. These electrons in their turn cause the electron-stimulated desorption of cryosorbed argon and tritium, which is redistributed along the CPS (migration process). This effect was modeled with the use of the method of angular coefficients. The main result is that the tritium migration process does not affect the CPS performance at KATRIN for a given inlet flow. Meanwhile, if the flow chosen is larger, the migration effect could be dominant.
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07.30.Cy Vacuum pumps
68.43.Rs Electron stimulated desorption
79.20.La Photon- and electron-stimulated desorption

Quantitative determination of reaction products by in-line thermal desorption spectroscopy: The system methanol∕Pd(111)

E. Demirci and A. Winkler

J. Vac. Sci. Technol. A 26, 78 (2008); http://dx.doi.org/10.1116/1.2816947 (5 pages) | Cited 2 times

Online Publication Date: 14 December 2007

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An evaluation procedure for the quantitative determination of thermal desorption products based on in-line mass spectrometry is described in detail. This procedure is, in particular, applicable for species which are pumped with high speed and, therefore, yield small signals in conventional mass spectrometry. The evaluation method was applied to the adsorption system methanol∕Pd(111). After dosing a Pd(111) surface at 140 K with methanol up to saturation of the chemisorbed layer, desorption of methanol, hydrogen, carbon monoxide, and water can be observed. The amount of all of the reaction products was determined quantitatively. The total number of adsorbed methanol was found to be 2.6×1014 MeOH/cm2, which is a lower limit, because coadsorbed water and hydrogen partially block adsorption sites on the surface. While 62% of the adsorbed methanol desorbs associatively, 38% of the adsorbed methanol dehydrogenate, resulting in desorption of hydrogen and carbon monoxide. No indication for C–O bond scission could be observed when methanol was adsorbed on the clean Pd(111) surface.
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68.43.Mn Adsorption kinetics
68.43.Vx Thermal desorption
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.47.De Metallic surfaces

Growth of ordered SrO layers on Si(100) using metal-organic surface reactions

B. G. Willis and A. Mathew

J. Vac. Sci. Technol. A 26, 83 (2008); http://dx.doi.org/10.1116/1.2819267 (7 pages) | Cited 1 time

Online Publication Date: 14 December 2007

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The formation of ordered alkaline earth metal-oxide layers on Si(100) through metal-organic surface reactions has been investigated. Strontium oxide layers were deposited on a thin (1.0±0.2 nm) SiO2 layer grown on Si(100) using a saturation coverage of the β-diketonate precursor bis(2,2,6,6-tetramethyl-3,5-heptanedionato)strontium [Sr(thd)2] followed by reaction with H2O. Oxide desorption at high temperatures (>800 °C) leads to an ordered strontium layer on the silicon surface. Auger electron spectroscopy, x-ray photoelectron spectroscopy, Rutherford backscattering spectrometry, and low-energy electron diffraction have been used to investigate the progress of the reaction. The data show a Sr/Si(100) surface with 3× order and a Sr coverage of (0.9±0.1)×1014/cm2. The observed metal coverage and ordering are explained by the saturation of the adsorbed metal-organic layer due to steric interactions that limit the adsorbed coverage. The results are promising for alternative methods to fabricate epitaxial oxides on silicon substrates.
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68.55.A- Nucleation and growth
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.65.-b Surface treatments

Effects of interfacial layer structures on crystal structural properties of ZnO films

J. S. Park, T. Minegishi, S. H. Lee, I. H. Im, S. H. Park, T. Hanada, T. Goto, M. W. Cho, T. Yao, S. K. Hong, and J. H. Chang

J. Vac. Sci. Technol. A 26, 90 (2008); http://dx.doi.org/10.1116/1.2821741 (7 pages) | Cited 12 times

Online Publication Date: 14 December 2007

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Single crystalline ZnO films were grown on Cr compound buffer layers on (0001) Al2O3 substrates by plasma assisted molecular beam epitaxy. In terms of lattice misfit reduction between ZnO and substrate, the CrN and Cr2O3/CrN buffers are investigated. The structural and optical qualities of ZnO films suggest the feasibility of Cr compound buffers for high-quality ZnO films growth on (0001) Al2O3 substrates. Moreover, the effects of interfacial structures on selective growth of different polar ZnO films are investigated. Zn-polar ZnO films are grown on the rocksalt CrN buffer and the formation of rhombohedral Cr2O3 results in the growth of O-polar films. The possible mechanism of polarity conversion is proposed. By employing the simple patterning and regrowth procedures, a periodical polarity converted structure in lateral is fabricated. The periodical change of the polarity is clearly confirmed by the polarity sensitive piezo response microscope images and the opposite hysteretic characteristic of the piezo response curves, which are strict evidences for the validity of the polarity controlling method as well as the successful fabrication of the periodical polarity controlled ZnO structure.
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68.55.ag Semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Charge-state distributions of metallic electron cyclotron resonance plasmas

P. Kumar, G. Rodrigues, P. S. Lakshmy, D. Kanjilal, and R. Kumar

J. Vac. Sci. Technol. A 26, 97 (2008); http://dx.doi.org/10.1116/1.2823486 (6 pages) | Cited 2 times

Online Publication Date: 14 December 2007

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The authors have developed metallic ion beams in the energy range of a few keV to a few MeV using a low-energy ion-beam facility (LEIBF) consisting of a 10 GHz all-permanent-magnet electron cyclotron resonance (ECR) ion source placed on a high-voltage (200 kV) platform. The metallic vapors were achieved by plasma sputtering, using a micro-oven and volatile compounds to produce multiply charged ECR plasma. The ions were then extracted from the plasma and their energy and momentum were analyzed using a high-resolution dipole magnet. Charge-state distributions (CSDs) of three metallic ECR plasmas (Cu, Ni, and Sn) produced by different techniques are presented to help in using low-energy metallic ions for implantation. We present the CSD studies of metallic ECR plasma and highlight the physics of the process involved.
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52.50.Qt Plasma heating by radio-frequency fields; ICR, ICP, helicons
52.50.Dg Plasma sources
52.77.Dq Plasma-based ion implantation and deposition

Numerical investigation via three-dimensional Monte Carlo modeling of sputtering and deposition processes in a direct current unbalanced magnetron discharge

R. Sobbia, P. K. Browning, and J. W. Bradley

J. Vac. Sci. Technol. A 26, 103 (2008); http://dx.doi.org/10.1116/1.2816940 (11 pages) | Cited 3 times

Online Publication Date: 17 December 2007

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A linked set of Monte Carlo applications has been developed in order to investigate the sputtering, deposition, and ionization processes in a circular direct current unbalanced magnetron discharge. Particles respond to prescribed electric and magnetic fields, the former taken from experimental measurements, and self-consistent plasma behavior resulting in changes in the fields is not accounted for. The motion of energetic electrons emitted from the target surface by ion impacts is followed in the gas phase in order to characterize ionization and excitation collisions and elastic scattering with argon filling gas. The inhomogeneous erosion track profile is computed and compared with experimental measurements. The transport of titanium sputtered neutrals between the target and substrate surfaces is then analyzed using both a rigid sphere collision model and an interatomic potential model to describe collisions between sputtered neutrals and background gas atoms. The radial emission distribution of sputtered atoms is taken from the electron transport model. The mean arrival energy and the angular distribution of titanium neutrals impinging on the substrate surface, and the metal density profile between target and substrate are calculated. Finally, the electron impact ionization of titanium neutrals in a plasma formed by a mixture of titanium (10% of argon density) and argon atoms is simulated, motivated by the promising possibility of controlling the deposition process by influencing the direction of the ion flux.
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68.55.at Other materials
81.15.Cd Deposition by sputtering
52.77.Dq Plasma-based ion implantation and deposition

Lithium manganese oxide films fabricated by electron beam directed vapor deposition

S. W. Jin and H. N. G. Wadley

J. Vac. Sci. Technol. A 26, 114 (2008); http://dx.doi.org/10.1116/1.2823488 (9 pages) | Cited 6 times

Online Publication Date: 17 December 2007

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Lithium manganese oxide thin films have been grown using a gas jet based, electron beam directed vapor deposition technique. The deposition rate could be controlled by the electron beam power as well as the gas jet density and speed. This enabled films to be grown at deposition rates up to 16 nm/s which is a significantly higher deposition rate than that reported for the growth of this material by sputtering and other vapor deposition techniques. The lithium manganese oxide films grown by this approach were slightly manganese deficient with a composition Li1+xMn2−yO4, where 0.08<x<0.125 and y ∼ 0.2. After annealing in air at 700 °C, thin films grown with a low jet speed had a cubic spinel structure and were composed of very small size grains. The small grain size resulted from the vapor phase formation of clusters and resulted in a nanocrystalline random film texture. These films were highly porous with a spongelike interconnected pore network. The use of a higher jet speed and lower growth pressure resulted in less vapor phase clustering. The films contained small, uniformly distributed pores and exhibited a significant ⟨111⟩ texture. These annealed films appeared well suited for use as the cathode layers in thin film Li/Li-ion batteries.
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68.55.at Other materials
68.55.jm Texture
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
82.45.Fk Electrodes
82.47.Aa Lithium-ion batteries
82.45.Yz Nanostructured materials in electrochemistry

Characterization of gaseous species in scanning atmospheric rf plasma with transmission infrared spectroscopy

Seong H. Kim, Jeong Hoon Kim, and Bang-Kwon Kang

J. Vac. Sci. Technol. A 26, 123 (2008); http://dx.doi.org/10.1116/1.2823483 (5 pages) | Cited 1 time

Online Publication Date: 20 December 2007

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A scanning atmospheric radio-frequency (rf) plasma was analyzed with transmission infrared (IR) spectroscopy. The IR analyses were made for the plasmas used for hydrophobic coating deposition and superhydrophobic coating deposition processes. Since the rf plasma was generated in a small open space with a high gas flow rate in ambient air, the density of gas-phase molecules was very high and the plasma-generated reactive species seemed to undergo various reactions in the gas phase. So, the transmission IR spectra of the scanning atmospheric rf plasma were dominated by gas-phase reaction products, rather than plasma-generated intermediate species. In the CH4/He plasma used for hydrophobic coating deposition, C2H6, C2H2, and a small amount of C2H4 as well as CO were detected in transmission IR. The intensities of these peaks increased as the rf power increased. The CO formation is due to the activation of oxygen and water in the air. In the CF4/H2/He plasma used for deposition of superhydrophobic coatings, C2F6, CF3H, COF2, and HF were mainly detected. When the H2/CF4 ratio was ∼ 0.5, the consumption of CF4 was the highest. As the H2/CF4 ratio increased higher, the C2F6 production was suppressed while the CF3H peak grew and the formation of CH4 were detected. In both CH4/He and CF4/H2/He plasma systems, the undissociated feed gas molecules seem to be highly excited vibrationally and rotationally. The information on plasma-generated reactive species and their reactions was deduced from the distribution of these gas-phase reaction products.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.80.Hc Glow; corona
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
52.77.Dq Plasma-based ion implantation and deposition

Two-stage flow-dividing system for the calibration of vacuum gauges

Hajime Yoshida, Kenta Arai, Hitoshi Akimichi, and Masahiro Hirata

J. Vac. Sci. Technol. A 26, 128 (2008); http://dx.doi.org/10.1116/1.2823481 (5 pages) | Cited 4 times

Online Publication Date: 21 December 2007

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A two-stage flow-dividing system was developed for calibrating an ionization gauge (IG) and residual gas analyzer (RGA). This system generates a stable high and ultrahigh vacuum from 8×10−3 to 2×10−7 Pa by adjusting the pressure in the first chamber using N2, Ar, He, and H2. The calibration pressure in the third chamber is calculated from the pressure in the second chamber using their linear relation in molecular flow. The uncertainty of the generated pressure was comparable to or several times larger than that of the continuous-expansion system. However, this system has a simple configuration and is easy to operate compared with the continuous-expansion system because it has no moving parts. Results of the calibration of IG and RGA showed that the two-stage flow-dividing system is useful for a routine calibration of practical vacuum gauges in high and ultrahigh vacuum.
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07.30.Dz Vacuum gauges
06.20.F- Units and standards

Growth and characterization of vanadium dioxide thin films prepared by reactive-biased target ion beam deposition

Kevin G. West, Jiwei Lu, Jiani Yu, David Kirkwood, Wei Chen, Yonghang Pei, John Claassen, and Stuart A. Wolf

J. Vac. Sci. Technol. A 26, 133 (2008); http://dx.doi.org/10.1116/1.2819268 (7 pages) | Cited 13 times

Online Publication Date: 2 January 2008

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Using a novel growth technique called reactive bias target ion beam deposition, the authors have prepared highly oriented VO2 thin films on Al2O3 (0001) substrates at various growth temperatures ranging from 250 to 550 °C. The influence of the growth parameters on the microstructure and transport properties of VO2 thin films was systematically investigated. A change in electrical conductivity of 103 was measured at 341 K associated with the well known metal-insulator transition (MIT). It was observed that the MIT temperature can be tuned to higher temperatures by mixing VO2 and other vanadium oxide phases. In addition, a current/electric-field induced MIT was observed at room temperature with a drop in electrical conductivity by a factor of 8. The current densities required to induce the MIT in VO2 are about 3×104 A/cm2. The switching time of the MIT, as measured by voltage pulsed measurements, was determined to be no more than 10 ns.
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68.55.aj Insulators
71.30.+h Metal-insulator transitions and other electronic transitions
73.61.Ng Insulators
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Synthesis and characteristics of new quaternary Ti–Mo–Si–N coatings by a hybrid coating system

Jin Woo Jeon, Seung Gyun Hong, Kwang Ryul Kim, and Kwang Ho Kim

J. Vac. Sci. Technol. A 26, 140 (2008); http://dx.doi.org/10.1116/1.2821730 (6 pages) | Cited 2 times

Online Publication Date: 2 January 2008

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Ternary Ti–Mo–N and new quaternary Ti–Mo–Si–N coatings were synthesized on substrates (AISI D2) and Si wafers by a hybrid coating system of an arc-ion plating technique using a Ti target and a dc magnetron sputtering technique using Mo and Si targets in N2/Ar gaseous mixture. The ternary Ti–Mo–N coatings were substitutional solid solutions of (Ti,Mo)N and showed maximum hardness of about 30 GPa at a Mo content of ∼ 10 at. %. With the addition of Si, the Ti–Mo–Si–N coating transformed into a nanocomposite consisting of fine (Ti,Mo)N crystallites and an amorphous Si3N4 phase. The hardness of the Ti–Mo–Si(8.8 at. %)–N coatings significantly increased to ∼ 48 GPa due to the microstructural change to the nanocomposite containing finer (Ti,Mo)N crystallites by the grain-size refinement effect of Si addition. The averaged friction coefficient of the Ti–Mo–Si–N coatings gradually decreased by increasing the Si content in the Ti–Mo–N coating. The microstructures of Ti–Mo–Si–N coatings were investigated with instrumental analyses of x-ray diffraction, x-ray photoelectron, and high-resolution transmission electron microscopy. In this work, the authors also investigated the effects of substrate bias voltage during deposition on the microstructure and mechanical property of Ti–Mo–Si–N coatings.
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68.55.A- Nucleation and growth
81.15.Cd Deposition by sputtering
68.55.J- Morphology of films
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.40.Pq Friction, lubrication, and wear
79.60.Dp Adsorbed layers and thin films

Synthesis and mechanical properties of CrMoCxN1−x coatings deposited by a hybrid coating system

Ji Hwan Yun, Su Jeong Heo, Kwang Ryul Kim, and Kwang Ho Kim

J. Vac. Sci. Technol. A 26, 146 (2008); http://dx.doi.org/10.1116/1.2821736 (5 pages) | Cited 6 times

Online Publication Date: 2 January 2008

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Quaternary CrMoCxN1−x coatings were deposited on steel substrates (AISI D2) and Si wafers by a hybrid coating system combining an arc-ion plating technique and a dc reactive magnetron sputtering technique using Cr and Mo targets in an Ar/N2/CH4 gaseous mixture. The carbon content of CrMoCxN1−x coatings was linearly increased with increasing CH4/(CH4+N2) gas flow rate ratio. The maximum hardness of 44 GPa was obtained from the CrMoCxN1−x coatings containing a carbon content of x = 0.33 with a residual stress of −4.4 GPa. The average friction coefficient of Cr–Mo–N coatings was 0.42, and it is decreased to 0.31 after applying CrMoCxN1−x coatings. This result was caused by the formation of a carbon-rich transfer layer that acted as a solid lubricant to reduce contact between the coating surface and steel ball. The microstructure of the coatings was investigated by x-ray diffraction, scanning electron microscopy, and x-ray photoelectron spectroscopy. In this work, the microstructure and mechanical properties of the CrMoCxN1−x coatings were systematically investigated with the instrumental analyses.
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68.55.A- Nucleation and growth
81.15.Cd Deposition by sputtering
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.40.Pq Friction, lubrication, and wear
68.60.Bs Mechanical and acoustical properties
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Surface roughening of silicon, thermal silicon dioxide, and low-k dielectric coral films in argon plasma

Yunpeng Yin and Herbert H. Sawin

J. Vac. Sci. Technol. A 26, 151 (2008); http://dx.doi.org/10.1116/1.2821747 (10 pages) | Cited 7 times

Online Publication Date: 2 January 2008

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The surface roughness evolutions of single crystal silicon, thermal silicon dioxide (SiO2), and low dielectric constant film coral in argon plasma have been measured by atomic force microscopy as a function of ion bombardment energy, ion impingement angle, and etching time in an inductively coupled plasma beam chamber, in which the plasma chemistry, ion energy, ion flux, and ion incident angle can be adjusted independently. The sputtering yield (or etching rate) scales linearly with the square root of ion energy at normal impingement angle; additionally, the angular dependence of the etching yield of all films in argon plasma followed the typical sputtering yield curve, with a maximum around 60°–70° off-normal angle. All films stayed smooth after etching at normal angle but typically became rougher at grazing angles. In particular, at grazing angles the rms roughness level of all films increased if more material was removed; additionally, the striation structure formed at grazing angles can be either parallel or transverse to the beam impingement direction, which depends on the off-normal angle. More interestingly, the sputtering caused roughness evolution at different off-normal angles can be qualitatively explained by the corresponding angular dependent etching yield curve. In addition, the roughening at grazing angles is a strong function of the type of surface; specifically, coral suffers greater roughening compared to thermal silicon dioxide.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.Cf Surface cleaning, etching, patterning
68.37.Ps Atomic force microscopy (AFM)
61.80.Jh Ion radiation effects
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
77.55.-g Dielectric thin films

Angular etching yields of polysilicon and dielectric materials in Cl2/Ar and fluorocarbon plasmas

Yunpeng Yin and Herbert H. Sawin

J. Vac. Sci. Technol. A 26, 161 (2008); http://dx.doi.org/10.1116/1.2821750 (13 pages) | Cited 5 times

Online Publication Date: 2 January 2008

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The angular etching yields of polysilicon in Cl2/Ar plasmas, and dielectric materials (thermal silicon dioxide and low-k dielectric coral) in fluorocarbon plasmas, have been characterized in an inductively coupled plasma beam apparatus. The effects of ion energy, feed gas composition, and plasma source pressure are studied. The experimental results showed that these etching parameters had a significant impact on the resulting angular etching yield curve. In particular, the angular etching yield curve was more sputteringlike at low plasma source pressure and/or low effective gas percentage (Cl2 and C4F8), with a peak around 60°–70° off-normal ion incident angle. In contrast, ion-enhanced-etching-like angular curves, which dropped gradually with off-normal angle, were formed at high plasma source pressure and/or high effective gas percentage. Further analysis indicated that the effective neutral-to-ion flux ratio reaching the surface was the primary factor influencing the angular etching yield curve. More specifically, the angular etching yield curve had physical sputtering characteristics at low neutral-to-ion flux ratios; while etching process was really dominated by ion-enhanced etching at high ratios and the angular curve was ion-enhanced-etching-like. The polymer deposition effects are also discussed in this article.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
77.55.-g Dielectric thin films
52.50.Dg Plasma sources

Lithium phosphorous oxynitride films synthesized by a plasma-assisted directed vapor deposition approach

Yoon Gu Kim and H. N. G. Wadley

J. Vac. Sci. Technol. A 26, 174 (2008); http://dx.doi.org/10.1116/1.2823491 (10 pages) | Cited 8 times

Online Publication Date: 2 January 2008

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A plasma-assisted directed vapor deposition approach has been explored for the synthesis of lithium phosphorous oxynitride (Lipon) thin films. A Li3PO4 source was first evaporated using a high voltage electron beam and the resulting vapor entrained in a nitrogen-doped supersonic helium gas jet and deposited on a substrate at ambient temperature. This approach failed to incorporate significant concentrations of nitrogen in the films. A hollow cathode technique was then used to create an argon plasma that enabled partial ionization of both the Li3PO4 vapor and nitrogen gas just above the substrate surface. The plasma-enhanced deposition process greatly increased the gas phase and surface reactivity of the system and facilitated the synthesis and high rate deposition of amorphous Lipon films with the N/P ratios between 0.39 and 1.49. Manipulation of the plasma-enhanced process conditions also enabled control of the pore morphology and significantly affected the ionic transport properties of these films. This enabled the synthesis of electrolyte films with lithium ion conductivities in the 10−7–10−8 S/m range. They appear to be well suited for thin-film battery applications.
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68.55.aj Insulators
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
66.30.H- Self-diffusion and ionic conduction in nonmetals
52.77.Dq Plasma-based ion implantation and deposition
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